U.S. patent application number 11/206074 was filed with the patent office on 2006-08-10 for method for operating a gas turbine.
Invention is credited to Jaan Hellat, Oliver Riccius, Richard Smith, Detlef Viereck.
Application Number | 20060174630 11/206074 |
Document ID | / |
Family ID | 32841940 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060174630 |
Kind Code |
A1 |
Hellat; Jaan ; et
al. |
August 10, 2006 |
Method for operating a gas turbine
Abstract
A method for operating a gas turbine (2), in particular in a
power plant, includes operating the gas turbine (2) with natural
gas. In order to adapt the gas turbine operation to different
natural gas qualities, a concentration of C.sub.2+ is measured in
the natural gas during gas turbine (2) operation. The gas turbine
(2) then is operated based on the current concentration of
C.sub.2+.
Inventors: |
Hellat; Jaan;
(Baden-Ruethihof, CH) ; Riccius; Oliver;
(Birmenstorf, CH) ; Smith; Richard; (Ennetbaden,
CH) ; Viereck; Detlef; (Lauchringen, CH) |
Correspondence
Address: |
CERMAK & KENEALY LLP
515 E. BRADDOCK RD
SUITE B
ALEXANDRIA
VA
22314
US
|
Family ID: |
32841940 |
Appl. No.: |
11/206074 |
Filed: |
August 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP04/50204 |
Feb 25, 2004 |
|
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|
11206074 |
Aug 18, 2005 |
|
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Current U.S.
Class: |
60/776 ;
60/39.465 |
Current CPC
Class: |
F23N 2221/10 20200101;
F02C 9/28 20130101; F05D 2270/083 20130101; F23N 2241/20
20200101 |
Class at
Publication: |
060/776 ;
060/039.465 |
International
Class: |
F02C 3/22 20060101
F02C003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2003 |
DE |
103 08 384.7 |
Claims
1. A method for operating a gas turbine which is supplied with
natural gas, the method comprising: measuring, during the operation
of the gas turbine, the C.sub.2+ concentration in natural gas that
is supplied to the gas turbine; and operating the gas turbine based
on the measured current concentration of C.sub.2+.
2. A method according to claim 1, comprising: measuring the
C.sub.3+ concentration in the natural gas during the operation of
the gas turbine; and wherein operating comprises operating the gas
turbine based on the measured current C.sub.2+ and C.sub.3+
concentrations.
3. A method according to claim 1, wherein a control procedure for
operating the gas turbine is adapted to the current C.sub.2+
concentrations.
4. A method according to claim 1, comprising: adapting at least one
operating parameter of the gas turbine to the current C.sub.2+
concentration.
5. A method according to one of the claim 1, comprising: with
increasing C.sub.2+ concentration, reducing -a flame temperature,
or reducing a turbine inlet temperature, or increasing a preheating
temperature, or combinations thereof.
6. A method according to claim 5, wherein said reduction of the
flame temperature, said reduction of the turbine inlet temperature,
or both, is carried out so that: a reference temperature that is
measured at a location subject to flashback remains constant; or a
pollutant emissions value, remains constant; or a position of the
flame front remains constant in a combustion chamber of the gas
turbine; or combinations thereof.
7. A method according to claim 6, comprising: measuring the
reference temperature at a burner or a natural gas injection
lance.
8. A method according to claim 1, wherein of operating the gas
turbine based on the current C.sub.2+ concentration comprises
operating above a preset control concentration.
9. A method according to one of the claim 1, comprising: generating
a warning signal when the current C.sub.2+ concentration exceeds a
preset alert concentration.
10. A method according to claim 9, wherein the alert concentration
is less than the control concentration.
11. A method according to claim 1, comprising: generating an
emergency signal when the current C.sub.2+ concentration exceeds a
preset maximum concentration.
12. A method according to claim 1: wherein operating the gas
turbine based on the current C.sub.2+ concentration comprises
operating above a preset control concentration which is
approximately 9 to 12 vol. % C.sub.2+ in natural gas; or comprising
generating a warning signal when the current C.sub.2+ concentration
exceeds a preset alert concentration which is approximately 7 to 10
vol. % (C.sub.2+ ) in natural gas; or comprising generating an
emergency signal when the current C.sub.2+ concentration exceeds a
preset maximum concentration which is approximately at least 16
vol. % C.sub.2+ in natural gas, or combinations thereof.
13. A method according to at least claim 4, wherein adapting
comprising adapting according to a characteristic diagram in which
a characteristic line is indicated for at least one operating
parameter that changes based on the C.sub.2+ concentration and that
shows the respective operating parameter as a function of C.sub.2+
concentration.
14. A method according to claim 13, wherein the characteristic
diagram for at least one operating parameter that is changed based
on the C.sub.2+ concentration contains at least two characteristic
lines that are allocated to different C.sub.3+ concentrations.
15. A method according to one of the claim 1, wherein measuring the
C.sub.2+ concentration comprises measuring with a gas-phase
chromatograph, a flame ionization detector, an infrared
spectrometer, or combinations thereof.
16. A gas turbine, comprising: a control device configured and
arranged to operate a gas turbine; a measuring device configured
and arranged to measure C.sub.2+ concentrations in natural gas when
supplied to the gas turbine; wherein the control device operates
the gas turbine based on the current C.sub.2+ concentration.
17. A gas turbine according to claim 16, wherein the measuring
device is configured and arranged to measure C.sub.3+
concentrations.
18. A method according to claim 1, wherein the gas turbine is part
of a power plant.
19. A method according to claim 6, wherein the pollutant emissions
value comprises a NO.sub.x emissions value.
20. A method according to claim 8, wherein the control
concentration is approximately 9 to 12 vol. % C.sub.2+ in natural
gas.
21. A method according to claim 9, wherein the alert concentration
is approximately 7 to 10 vol. % C.sub.2+ in natural gas.
22. A method according to claim 11, wherein the maximum
concentration is approximately at least 16 vol. % C.sub.2+ in
natural gas.
23. A power plant comprising a gas turbine according to claim 16.
Description
[0001] This application is a Continuation of and claims priority
under 35 U.S.C. .sctn. 120 to International application number
PCT/EP2004/050204, filed 25 Feb. 2004, and claims priority under 35
U.S.C. .sctn. 119 to German patent application number 103 08 384.7,
filed 27 Feb. 2003, the entireties of both of which are
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method for operating a
gas turbine, in particular in a power plant.
[0004] 2. Brief Description of the Related Art
[0005] Usually gas turbines are fueled with natural gas. Natural
gas is mainly comprised of CH.sub.4 (methane). Furthermore, natural
gas also contains so-called non-CH.sub.4 components that can be
diluting or enrichment substances. Examples of diluting substances
are N.sub.2 (nitrogen) and CO.sub.2 (carbon dioxide). Enrichment
substances usually are higher saturated hydrocarbons such as
C.sub.2H.sub.6 (ethane), C.sub.3H.sub.8 (propane), butane, etc.
[0006] Currently it is customary to characterize the quality, i.e.,
the composition of natural gas, by using two indices. These are the
calorific value on one hand and the Wobbe index on the other hand.
Up until now it furthermore has been customary to operate gas
turbines with natural gas of consistent quality.
[0007] Today gas supply companies are not yet able to guarantee
consistent quality for the natural gas they supply. As part of the
liberalization of the natural gas market, natural gas suppliers
increasingly attempt to optimize natural gas demand and natural gas
prices. The result is that natural gas is obtained from different
sources, is mixed and supplied to the consumers. This in turn
results in a high degree of variability of the natural gas with
regard to quality and/or composition. The composition of natural
gas in turn can influence the combustion process in gas turbines.
The indices known up until now (calorific value and Wobbe index)
are not suitable to describe these effects on the operation of gas
turbines with the necessary degree of accuracy. Therefore, power
plant operators must be prepared for varying natural gas quality in
the future.
SUMMARY OF THE INVENTION
[0008] This is where the invention would like to offer a remedy.
One aspect of the present invention provides an improved embodiment
for a gas turbine or for a related operating method that above all
would allow accommodating different natural gas qualities.
[0009] One principle of the present invention includes the general
idea of measuring the current composition of the natural gas
supplied to the gas turbine during the operation, i.e., online, and
of adapting the operating concept of the gas turbine to the
respective current natural gas composition. Substantial for the
invention is the fact that the composition of the natural gas is
characterized based on the share or the concentration of C.sub.2+
in the natural gas. C.sub.2+ is the abbreviation for all higher
saturated hydrocarbons, i.e., all hydrocarbons with the exception
of CH.sub.4. The invention utilizes the knowledge that it suffices
to measure the concentration of C.sub.2+ in an integral manner in
order to obtain a sufficient characterization of the natural gas
composition. Above all it is not necessary to determine the
concentration of individual dilution substances. Furthermore, as a
rule, it is not necessary to separately determine the
concentrations of C.sub.2H.sub.6, C.sub.3H.sub.8, etc. This results
in an extreme simplification for the determination of another index
that characterizes the quality of natural gas, namely the
concentration of C.sub.2+.
[0010] An increase in C.sub.2+ concentration in natural gas results
in an ignition delay time decrease, as well as spontaneous ignition
temperature decrease in the combustion process of the gas turbine
that is supplied with this natural gas. Furthermore, the
concentration of C.sub.2+ affects the upper and lower mixing limit
for inflammable natural gas and air mixtures. Furthermore, the
C.sub.2+ concentration can have an effect on the chemical reaction
path, which in turn changes the burn-out degree and the emission
values of the combustion reaction. Additionally, a change in the
C.sub.2+ concentration can effect a change in the Wobbe index
and/or the calorific value, which can be used to influence the
injection impulse and the mixing properties of natural gas and
combustion air. For example, in a typical premix combustion system
this means that the position of a reaction zone depends on the
quality of the natural gas. This means that the flame front in the
gas turbine combustion approaches the burner with increasing
C.sub.2+ concentration. Therefore, an increase in C.sub.2+
concentration consequently increases the chances of a flashback and
an overheating of the burner, which in turn can lead to an increase
in pollutant emissions, especially NO, emissions.
[0011] In order to be able to differentiate the effects of the
C.sub.2+ content in natural gas on the gas turbine process, a
further development of the method in accordance with the invention
proposes to also measure C.sub.3+ concentrations that are present
in the natural gas during the operation of the gas turbine and to
operate the gas turbine based on the current concentrations of
C.sub.2+ and C.sub.3+. Corresponding to the definition of C.sub.2+,
the abbreviation C.sub.3+ stands for all hydrocarbons, except
CH.sub.4 and C.sub.2H.sub.6. By also measuring the C.sub.3+
concentration, it is possible to consider the influence of
C.sub.2H.sub.6 on the gas turbine operation by itself. Such
correlation can advantageously be taken into account for the
proposed further development.
[0012] Other important characteristics and advantages of the
present invention are disclosed in the drawings and the respective
description of the figures based on the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings show preferred exemplary embodiments of the
invention and are described in more detail in the following
description.
[0014] The following is shown schematically:
[0015] FIG. 1 a wiring diagram-type presentation of the principle
of a gas turbine facility,
[0016] FIGS. 2 through 4 various characteristic diagrams for gas
turbine operating parameters.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0017] According to FIG. 1, a gas turbine facility 1, especially in
a power plant, includes at least one gas turbine 2 that is supplied
with natural gas via a natural gas supply line 3. A control device
4 in which a suitable control procedure is carried out is arranged
for operating the gas turbine 2. The control device 4 and/or the
control procedure check the operating parameters of the gas turbine
2, such as the flame temperature of the combustion process in the
combustion chamber of the gas turbine 2. Furthermore, it is
possible to check the turbine inlet temperature as well as other
temperatures. In addition, it is possible to check pollutant
emissions, in particular NO.sub.x emissions. It also is possible to
monitor the position of the flame front in the combustion chamber.
The control device 4 and/or its procedure usually are utilized to
operate the gas turbine 2 on a constant level at a pre-determined
nominal operating point. In doing so, additional adjustments for
changing load conditions (e.g. peak loads) are possible.
[0018] According to the invention, the gas turbine facility 1
additionally is equipped with a measuring device 5 with which
C.sub.2+ concentrations in the natural gas that is being fed into
the gas turbine 2 can be measured. For this purpose the measuring
device 5 is connected to the natural gas supply line 3 in 6. The
measuring results, i.e., the C.sub.2+ concentration, then are
transmitted to the control device 4 via a corresponding signal or
data transmission line 7 and are processed by the control device
and/or its procedure. The control device 4 then operates the gas
turbine 2 based on the current C.sub.2+ concentration. The
corresponding control signals are transmitted via a control signal
line 8.
[0019] The measuring device 5 can have a gas-phase chromatograph
that works relatively slowly, for example. Such a gas-phase
chromatograph has a delay time of several minutes. If changes in
the gas composition or C.sub.2+ concentration are to be recorded
faster, it is also possible to use other suitable devices, such as
a flame ionization detector or an infrared spectrometer, for
example, that respond within seconds.
[0020] When measuring the C.sub.2+ concentration, the total share
of all higher saturated hydrocarbons is measured and combined in an
integral concentration. In order to be able to take the effects of
C.sub.2H.sub.6 concentrations in natural gas into account in a
differentiated manner, it is possible to separately record the
C.sub.2H.sub.6 concentration as well. However, it is easier to use
a method in which the integral concentration of C.sub.3+ in
addition to the concentration of C.sub.2+ is determined. The
difference then corresponds to the concentration of
C.sub.2H.sub.6.
[0021] In a further development, the control device 4 can therefore
operate the gas turbine 2 based on the C.sub.2+ and C.sub.3+
concentrations. This type of differentiation in principle can be
even more refined, for example, by also measuring the C.sub.4+
concentration, which allows for an isolated consideration and
taking into account of the influence of C.sub.4H.sub.8.
[0022] It is important to note that the respective concentration,
especially that of C.sub.2+ and C.sub.3+, is determined while the
gas turbine 2 is operated, i.e. more or less online, in order to be
able to adapt the operation of the gas turbine 2 to changing
concentrations of C.sub.2+ and/or C.sub.3+ as quickly as
possible.
[0023] The adjustment of the operation of the gas turbine 2 to the
current concentrations of C.sub.2+ and/or C.sub.3+ suitably occurs
by varying at least one operating parameter of the gas turbine 2
based on the current concentrations of C2+ and/or C.sub.3+.
Operating parameters that are especially suitable for an adjustment
of the gas turbine operation to the current concentrations of
C.sub.2+ and/or C.sub.3+ are, for example, flame temperature
T.sub.F, as well as a turbine inlet temperature T.sub.IT.
Therefore, an embodiment is preferred in which the control device 4
or its procedure reduce the flame temperature T.sub.F and/or the
turbine inlet temperature T.sub.IT with increasing concentrations
of C.sub.2+ and/or C.sub.3+. As explained above, an increasing
concentration of C.sub.2+ and/or C.sub.3+ results in a shortening
of the ignition delay time and a reduction in the spontaneous
ignition temperature of the natural gas. The reduction in the flame
temperature T.sub.F and/or the turbine inlet temperature T.sub.IT
counteracts this and results in a certain offset.
[0024] Of special interest is an embodiment in which the reduction
of the flame temperature T.sub.F and/or the turbine inlet
temperature T.sub.IT is or are carried out in a manner that ensures
that a suitable reference temperature that is checked by the
control device 4 remains substantially constant. A point that is
subject to flashbacks is especially suitable for measuring such a
reference temperature. For example, the reference temperature can
be measured on or in a burner and/or on a lance for the injection
of the natural gas.
[0025] The adjustment of the flame temperature T.sub.F and/or the
turbine inlet temperature T.sub.IT to the current concentrations of
C.sub.2+ and/or C.sub.3 can be carried out additionally or
alternatively in a manner that ensures that a pollutant emissions
value, preferably for NO, emissions, remains mainly constant. In
addition or alternatively, the resetting of the flame temperature
T.sub.F and/or the turbine inlet temperature T.sub.IT can occur in
a manner that ensures that the position of the flame front in the
combustion chamber remains substantially constant.
[0026] FIG. 2 shows a characteristic diagram 9 in which a
characteristic line 10 is indicated. This characteristic line 10
describes the functional connection between the flame temperature
T.sub.F and/or the turbine inlet temperature T.sub.IT that is
entered on the ordinate and the concentration of C.sub.2+ in the
natural gas that is entered on the abscissa. The flame temperature
T.sub.F and/or the turbine inlet temperature T.sub.IT represent the
operating parameters of the gas turbine 2 that are set and checked
by the control device 4. As discussed above, it is advantageous for
the operation of the gas turbine to lower the flame temperature
T.sub.F and/or the turbine inlet temperature T.sub.IT with
increasing C.sub.2+ concentration.
[0027] As rule the adjustment of the above operating parameters
T.sub.F and/or T.sub.IT can be carried out continuously. However,
an embodiment is practical in which an adjustment of the indicated
operating parameters T.sub.F, T.sub.IT only occurs above a control
concentration K.sub.control of C.sub.2+ in natural gas. This means
that at C.sub.2+ concentrations below control concentration
K.sub.control, the flame temperature T.sub.F and/or the turbine
inlet temperature T.sub.IT remain constant in the characteristic
line 10. Starting with this control concentration K.sub.control the
respective operating parameter T.sub.F, T.sub.IT is reduced with
increasing C.sub.2+ concentration. This reduction can be continuous
in accordance with the solid characteristic line 10. The dotted
line, on the other hand, indicates a discontinuous or incremental
variation of the characteristic line 10' at which the respective
operating parameter T.sub.F, T.sub.IT incrementally follows the
current value of the C.sub.2+ concentration.
[0028] In addition, characteristic line 9 [sic] contains an alert
concentration K.sub.alert that is smaller than the control
concentration K.sub.control. As soon as the current C.sub.2+
concentration exceeds this alert concentration K.sub.alert, the
control device 4 emits a corresponding warning signal that can be
processed accordingly. This alert concentration K.sub.alert can be
such that it takes into account inaccuracies and delay times for
measuring the C.sub.2+ concentration.
[0029] Furthermore, a maximum concentration K.sub.maximum that is
larger than the control concentration K.sub.control is entered in
characteristic diagram 9. As soon as the C.sub.2+ concentration
reaches or exceeds the maximum concentration K.sub.maximum, the
control device 4 generates an emergency signal that can be
processed in a suitable manner. In extreme cases, for example, the
gas turbine 2 can be shut down.
[0030] The above concentrations K.sub.control, K.sub.alert,
K.sub.maximum are preset and can be determined empirically or based
on calculation models, for example.
[0031] Control concentration K.sub.control can have a value of 9 to
12 vol. % C.sub.2+ in natural gas, for example. The alert
concentration K.sub.alert can have a value between 7 and 12 vol. %
C.sub.2+ in natural gas, for example. A value of at least 16 vol. %
in natural gas can be preset for maximum concentration
K.sub.maximum.
[0032] If, in addition to the C.sub.2+ concentration, the C.sub.3+
concentration in natural gas is determined and evaluated as well,
it might be practical to place several characteristic lines 10 in
characteristic diagram 9 as shown in FIG. 3 in order to indicate
the dependence between the respective operating parameter (e.g.
flame temperature T.sub.F and/or turbine inlet temperature TIT) and
the concentration of C.sub.2+. These characteristic lines 10
correspond to different concentrations of C.sub.3+, which is
indicated by an arrow 11 in FIG. 3. The C.sub.3+ concentration
increases in the direction of the arrow. For the control device 4
this means that the correct characteristic line 10 must be selected
depending on the current C.sub.3+ concentration, and then the
correct operating parameter such as T.sub.F and/or TIT is
determined based on the selected characteristic line 10, depending
on the current C.sub.2+ concentration. According to FIG. 3, the
different characteristic lines 10 in characteristic diagram 9
accordingly are assigned different control concentrations
K.sub.control , as well as different maximum concentrations
K.sub.maximum, while alert concentration K.sub.alert is the same
for all characteristic lines 10.
[0033] While in the above examples flame temperature T.sub.F and
turbine inlet temperature T.sub.IT are given as examples of
operating parameters that can be adapted alternatively or
cumulatively, depending on the current C.sub.2+ and/or C.sub.3+
concentrations, it is clear that the present invention is not
limited to influencing these operating parameters. FIG. 4 therefore
shows examples of an additional operating parameter that can be
adjusted, depending on the current concentrations of C.sub.2+
and/or C.sub.3+.
[0034] It was found that the C.sub.2+ concentration and to an even
greater degree the C.sub.3+ concentration influences the dew point
of natural gas, and an increasing concentration of higher saturated
hydrocarbons results in an increase of the dew point temperature.
In order to avoid the development of condensation in the fuel
distribution system of gas turbine 2, it is therefore practical to
adapt a preheating temperature T.sub.P of the natural gas to the
current C.sub.2+ and/or C.sub.3+ concentrations.
[0035] Accordingly, FIG. 4 shows a characteristic line 13 in
another characteristic diagram 12 that reflects the correlation
between the preheating temperature T.sub.P (ordinate) and in this
case the C.sub.3+ concentration (abscissa). The control device 4
accordingly causes an increase in the preheating temperature
T.sub.P of the natural gas with increasing C.sub.3+ concentration
and starting with control concentration K.sub.control . The risk
that condensation might form is therefore reduced due to an
increasing dew point temperature.
LIST OF REFERENCES
[0036] 1 gas turbine facility [0037] 2 gas turbine [0038] 3 natural
gas supply line [0039] 4 control device [0040] 5 measuring device
[0041] 6 measuring point [0042] 7 signal or data transmission line
[0043] 8 control line [0044] 9 characteristic diagram [0045] 10
characteristic line [0046] 11 arrow [0047] 12 characteristic
diagram [0048] 13 characteristic line [0049] F.sub.T flame
temperature [0050] T.sub.IT turbine inlet temperature [0051]
T.sub.P preheating temperature [0052] C.sub.2+ concentration of
C.sub.2+ [0053] C.sub.3+ concentration of C.sub.3+ [0054]
K.sub.alert alert concentration [0055] K.sub.control control
concentration [0056] K.sub.maximum maximum concentration
[0057] While the invention has been described in detail with
reference to exemplary embodiments thereof, it will be apparent to
one skilled in the art that various changes can be made, and
equivalents employed, without departing from the scope of the
invention. Each of the aforementioned documents is incorporated by
reference herein in its entirety.
* * * * *